The herring, Clupea harengus, in common with other clupeoids, has ducts between the swimbladder and the exterior and has no apparent gas secretion organs. Experiments under pressure show that the central regions of the swimbladder wall are very compliant and collapse as the fish moves deeper in the sea, leaving the end sections patent. Gas is thus always held where it is available to maintain the gas-filled bulla system.

The information received by a fish about a vibrating source will depend on the patterns of excitation of various groups of receptors. Sprats, herrings and other clupeoids have bullae containing gas which are closely related to the sense organs of the utriculi, sacculi and the lateral lines. Structures of particular relevance to the functioning of thissystem are described and an account of their mechanical responses to low frequency pressure stimuli is given.

The mechanical responses of several structures in the auditory and lateral-line systems of the sprat Sprattus sprattus(L.) and the herringClupea harengus L. to oscillatory pressure changes have been observed over a range of frequencies from 0·014 t0 2600 Hz. The pressures required to give constant responses of the bulla membrane, and the lateral recess membrane varied relatively little between 0·014 and 1000 Hz; above 1000 Hz the sensitivity fell quickly as frequency increased.

Traditional scale reading methods have been compared with [C]glycine uptake data to study scale growth in bass.

Both methods are capable of being used to age young fish and determine their rate of growth. The glycine incorporation rate is, however, of more value in studying shortterm changes in fish growth. When applied in this way, it indicates that the apparent isometric relationship between scale and body length is actually the sum of a number of allometric interactions. Some of the errors that can occur in scale reading are demonstrated by the application of these methods.

The ultrastructure and dimensions of the solenocytes of Branchiostoma lanceolatum are reviewed briefly. The functional ability of these units is calculated upon theoretical grounds in a manner similar to that applied to flame cells. Their more delicate construction would suggest that Branchiostoma would have great difficulty in maintaining any significant osmotic pressure difference between the medium and its body fluids.

The bristle-bearing receptors on either side of the trunk in Oikopleura are connected to the caudal ganglion by the axons of central cells which form electrical synapses (gap junctions) at the bases of the receptor cells. The same axons also form similar synapses with epithelial cells adjacent to the receptors. Direct mechanical stimulation of the receptor processes evokes changes in the locomotor rhythm of the same kind as evoked by action potentials propagated in the epithelial cells. This remarkable arrangement is suggested to be a consequence of the reduced numbers of cells in larvaceans.

This paper describes a new asterinid starfish found first in southern Britain, but now also known from the Mediterranean and the Adriatic. Detailed comparison is made between the new species and the closely related Asterina gibbosa in terms of morphology, reproductive biology and life-history. The new species is adapted for life on the upper parts of rocks and on perennial algae in intertidal rock pools; it is small in size, matures early, lays large eggs, broods its young and has a short life span.

Crassostrea gigas (Thunberg) and Ostrea edulis L. were grown at sustained temperatures of 12°, 15°, 18° and 21°C for a period of 19 weeks. Regular assays of weight specific ammonia excretion rate were made, following which animals were sacrificed for estimation of dry meat weight, dry shell weight, biochemical composition (percentage carbon, nitrogen, carbohydrate, ash) and gonadal development (histological assessment). Crassostrea gigas grew from an intial live weight of 5·2 g to values of 23·5, 28·2, 34·6 and 38·7 g at 120, 150, 180 and 21 °C respectively.

Scanning electron and optical microscopic examination of the hinge apparatus and primary ligament pit of two Recent mytilids (Mytilus edulis and Modiolus modiolus) revealed a similar sequence of ontogenetic changes in both species from the prodissoconch I stage through metamorphosis. Hinge-line dentition was absent at the prodissoconch I stage. Provinculum length and complexity increased throughout larval development with progressive lateral thickening characteristic of the family Mytilidae.

The salinity of the water retained within the mantle cavity of mussels after the shell valves have closed in response to falling environmental salinities is influenced by the rate of external salinity change. At high rates of salinity change the retained water salinity is significantly higher than in animals exposed to slowly changing salinities. However, the mantle fluid salinity is not primarily determined by the timing ofx shell valve adduction, but by closure of the exhalant siphon.

Adult and larval stages of Siboglinum fiordicum, collected from 32 to 35 m depth, accumulate measurable quantities of amino acids and glucose from low concentrations. The amino acids are absorbed against a considerable gradient. The glucose and the amino acids are metabolized in the tissues and substantial amounts are respired to give carbon dioxide or volatile organic acids. Under the experimental conditions almost all the metabolism follows aerobic pathways.

A compilation has been made of new data on the distribution of the deep-water coralLophelia pertusa(L.) derived from trawling records, grab and dredge stations and submersible dives, together with the few published records. The coral is widely distributed and occurs on all the offshore banks of the north-east Atlantic, with some records from the deepest water of the Minches and Sea of the Hebrides.

Submersible observations have been made on‘ patches’ of the deep-water coral Lophelia pertusa (L.) occurring on Rockall Bank, north-east Atlantic. It is suggested that an initial colony gives rise to a ring of younger colonies. These in turn give rise to further rings of colonies, thus enlarging the ‘patch’. The transition from stage to stage depends on portions of living colonies, weakened by clionid sponge attacks, breaking off and falling away from the colony so providing the substrate for the development of later colonies, thus enabling lateral increase in the size of the ‘patch’ to take place.

A new member of the Chrysophyceae, Rhizochromulina marina gen. et sp.nov. is described by means of both light and electron microscopy of cultured material. Vegetative cells are non-flagellate and amoeboid with many fine beaded filipodia and a single golden-brown chloroplast. Zoospores are fusiform in shape and genuinely uniflagellate with no emergent vestigial second flagellum. They appear to possess the most reduced and phylogenetically advanced type of motile cell organization yet found in the Chrysophyceae.

A strain of Zooxanthella microadriatica (Freudenthal) comb.nov. has been isolated from decaying Chondrus crispus (L.) Stackh. The ultrastructure of this isolate has been compared to that of Z. microadriatica inhabiting Cassiopea Peron and Lesueur, 1809, sp. In an aqueous medium the cell cycle of both isolates consists of a coccoid non-motile phase alternating with a thecate motile phase.

A species believed to be more primitive than C. natans (Grontved) (type species of Calliacantha Leadbeater) has been described and illustrated by means of light and electron microscopy of dry whole mounts prepared in situ from freshly gathered sea water, mainly in South Africa but supplemented by one gathering from Britain.

In the Acantharia, two different symbiotic algae are known. One is a dinoflagellate with a typical mesocaryon and the other, studied here, exhibits the characters of the Prymnesiophyceae (Haptophyceae).

Detailed descriptions of the non-motile and presumed premotile stages of this symbiont are given, with special reference to the haptonema, the scales and the plastid.

Comparisons are made with other members of the Prymnesiophyceae and the systematic position of the symbiotic alga is discussed.

Two benthic Rhodophyta, Ceramium pedicellatwn and Neogardhiella baileyi, were cultured in the laboratory to investigate uptake and subsequent release of Cu by both living and decomposing thalli. Concentration factors of Cu in the thalli of 4540-6864 were obtained. Algae grown initially in copper-supplemented media were cultured for 7 days in organic free medium and the amounts of Cu associated with the dissolved inorganic and organic fractions were then determined.

The seasonal variations of dissolved inorganic and organic N and P in the waters of the English Channel during an 11-year study are discussed. The N results show that as NO3 is utilized by phytoplankton there is an increase in the concentration of the dissolved organic N fraction and there are always significant amounts of dissolved N in some form in the water.

The small acoele Convoluta roscoffensis Graff occurs locally in abundance in suitable intertidalareas of wet sand from the Channel Islands and the coast of Brittany southwards along the westcoast of France (Holligan and Gooday, 1975). The species is well known for its uniquely intimate symbiosis with Platymonas convolutae Parke et Manton: after initial ingestion of the living alga by hatching ‘ white’ worms the animal comes to depend entirely on the algal cells contained in its tissues for its nutrition (Holligan and Gooday, 1975).